Shane Jones asked why recreational fishing limits had been cut when there appeared to be surplus fish in the commercial supply chain. Photo / APN

Supermarket giant Countdown is facing fresh questions after large bins of whole snapper found at a waste meat processing plant were traced to its supply chain.

The fish were found at a Waikato rendering plant which turns it into fish meal and fish oil. A docket found with the bins shows 6.7 tonnes of fish were delivered to Waikato By Products in January.

A fisherman who discovered the fish at the company's Tuakau base found the docket on a visit, during which he filmed new deliveries of fish to the plant. The docket describes the origin of the fish as "Prog - Penrose".

Progressive, which runs Countdown supermarkets, has confirmed fish considered "unfit for human consumption" is turned into fertiliser but says the amount is small.

A spokeswoman for Countdown denied there was any dumping. "I'm sure you can gather it just doesn't make commercial sense for us to dump fish."

Instead, she said 0.2 per cent of fish in its supply chain over the past year was rendered down to fish meal or fish oil.

"We work daily to manage our fish supply and ensure we have the right amount for our stores every day. If we have extra product, we will always sell this through our stores at a discount, so that there is no wastage."

Countdown currently has snapper fillets for sale at $38.99 a kilogram.

The supermarket chain is already under scrutiny after a complaint from Labour MP Shane Jones to the Commerce Commission following allegations of anti-competitive behaviour. The discovery of the discarded fish has prompted Mr Jones to demand an investigation.

The MP was shown footage of the fish by Maori TV's Native Affairs show, which will screen it tonight as part of an investigation into the practice.

In a letter to Primary Industries Minister Nathan Guy, Mr Jones asked why recreational fishing limits had been cut when there appeared to be surplus fish in the commercial supply chain.

"If waste is occurring you should act. After all, how will dumping contribute positively to the rebuilding of the fishery? I request that you conduct a thorough review to assure Kiwis that all regulations are being observed in the face of this dumping. At a time when recreational fishers are being asked to make a sacrifice it would appear that supermarkets are grasping at profit to the detriment of the snapper fishery," he wrote.